Casting method to produce a casting and press used for the casting method

Abstract

A casting method to produce a casting and a press used for the casting method, using a mold which forms a cavity in a shape of a casting, so as to produce a casting by overlapping a lower mold with an upper mold, which molds are molded by a molding method, the casting method comprises the steps of: pouring into the lower mold a quantity of molten metal required to produce a casting; lowering the upper mold at a predetermined first speed until the upper mold reaches a predetermined position just before the upper mold starts contacting a surface of the molten metal; lowering the upper mold at a predetermined second speed after the upper mold is further lowered beyond the predetermined position; detecting and obtaining information on the status of the upper mold which overlaps the lower mold; and stopping the lowering of the upper mold when detecting the information on the status of the upper mold that shows that the predetermined conditions are met.

1. A press for producing a casting from molten metal in a mold, said press comprising:
 a movable frame; 
 an up-and-down means having a rod attached to the movable frame; 
 a plate connected to an end portion of the rod of the up-and-down means; 
 guide rods that extend perpendicularly upward from the plate and slide with respect to the moveable frame to guide the plate when the plate is moved up and down by the up-and-down means; 
 an upper molding flask containing an upper sand mold having a convex portion; 
 a fixing means attached to the plate to fix the upper molding flask thereto so that the convex portion of the upper sand mold faces downward; 
 a fixed lower molding flask containing a lower sand mold having a concave portion facing upward and corresponding to the convex portion of the upper sand mold so that a cavity in the shape of a casting is formed when the upper sand mold is overlapped and pressed onto the lower sand mold to form a mold; 
 a detection means attached to the end portion of the rod of the up-and-down means for detecting and obtaining information on the status of the upper sand mold, which upper sand mold is caused to overlap and be pressed against the lower sand mold by downward movement of the plate by the up-and-down means after molten metal has been poured into the convex portion of the lower sand mold; 
 operation circuits for controlling movement of the movable frame, lifting and lowering movement of the up-and-down means, the fixing means, and the movement of the up-and-down means based on the information detected and obtained by the detection means, 
 wherein the operation circuit for the up-and-down means has an input circuit that sets a speed of the up-and-down means at a predetermined first downward speed until the upper sand mold is lowered to a predetermined position just before the upper sand mold starts contacting a surface of molten metal in the lower sand mold, and then sets a speed of the up-and-down means at a predetermined second speed after the upper sand mold is further lowered beyond the predetermined position to overlap and press the upper sand mold against the lower sand mold and form the mold in which a casting is produced in said cavity; and 
 a memory circuit that stores the information on the status of the upper mold, which is information on the pressure that the upper sand mold receives from the molten metal and the lower sand mold or a distance that the upper sand mold descends. 
 
     
     
       2. The press according to  claim 1 , wherein the memory circuit stores a preset formula expressing a relationship of a weight of the casting and the second speed, and the input circuit sets the second speed to a speed that suitably corresponds to the weight of the casting. 
     
     
       3. The press according to  claim 2 , wherein the formula is a quadratic curve that shows that the weight of the casting decreases as the second speed increases. 
     
     
       4. The press according to  claim 2  or  3 , wherein the second speed is within ±85-88% of the mid-point of the second speed as defined by the formula expressing the relationship of the weight of the casting and the second speed.